brodidit for students
Home / Practice / Class 9 / Mathematics / Real and complex numbers
Real and complex numbers
10 Class 9 Mathematics questions with answers and explanations.
Printable worksheet with answer key
-
Which of these is an irrational number?
- 1 The square root of 2
- 2 4
- 3 3/4
- 4 0.5
Show answer
Correct answer: The square root of 2
The square root of 2 cannot be written as a ratio of two integers.
-
What is i squared, where i is the imaginary unit?
- 1 0
- 2 -1
- 3 i
- 4 1
-
What is (2 + 3i) + (4 - i)?
- 1 2 + 2i
- 2 8 + 3i
- 3 6 + 4i
- 4 6 + 2i
Show answer
Correct answer: 6 + 2i
Add real parts: 2 + 4 = 6. Add imaginary parts: 3 - 1 = 2.
-
What is the conjugate of 3 + 4i?
- 1 -3 + 4i
- 2 3 - 4i
- 3 -3 - 4i
- 4 4 + 3i
Show answer
Correct answer: 3 - 4i
The conjugate changes the sign of the imaginary part.
-
Which property is shown by a + b = b + a?
- 1 Commutative
- 2 Associative
- 3 Identity
- 4 Distributive
Show answer
Correct answer: Commutative
Changing the order of addition does not change the result: the commutative property.
-
What is the additive identity of real numbers?
- 1 0
- 2 Infinity
- 3 -1
- 4 1
-
Which of these is a natural number?
- 1 0.7
- 2 7
- 3 7/3
- 4 -7
-
The product of a rational and an irrational number (non zero rational) is:
- 1 Rational
- 2 Irrational
- 3 Integer
- 4 Zero
Show answer
Correct answer: Irrational
For example 2 times the square root of 2 is irrational.
-
What is (3 + 2i) - (1 + 5i)?
- 1 4 - 3i
- 2 2 - 3i
- 3 2 + 3i
- 4 4 + 7i
-
Which number is both rational and an integer?
- 1 1/2
- 2 5
- 3 Square root of 2
- 4 pi